1. Field of the Invention
The present invention relates to a toner cartridge and an image forming apparatus including the same.
2. Description of the Related Art
An image forming apparatus for forming an image using electrophotography is able to form a high quality image with a simple operation and maintenance thereof is easy, and therefore, is used for a copier, a printer, a facsimile and the like to be widely prevalent. A general electrophotographic image forming apparatus is comprised mainly of an image bearing member on which an electrostatic latent image is to be formed, a developing section which develops the electrostatic latent image with a toner, a transfer section which transfers the developed toner image onto recording paper, and a fixing section which fixes the toner image transferred onto the recording paper.
In this manner, in the image forming apparatus using the toner, it is necessary to replenish the toner when the toner contained in the apparatus is consumed to be exhausted. Since the toner is an aggregate of toner particles which are extremely fine and light-weight, when the toner is replenished to the image forming apparatus, the toner particles are likely to scatter in the air, thus the apparatus itself and surroundings thereof become contaminated in some cases. Accordingly, in recent years, a method of replacing an entire toner cartridge using a container-like toner cartridge capable of containing the toner inside thereof, that is, a method of detaching the toner cartridge running out of the toner from a main body of the image forming apparatus and attaching a new toner cartridge filled with a toner is prevailing.
FIG. 16 is a cross-sectional view showing an unused toner cartridge 200 according to a conventional art. The toner cartridge 200 which is unused, that is, in an initial state is attached to the main body of the image forming apparatus replacing the toner cartridge that has been already attached to the main body of the image forming apparatus running out of the toner.
The toner cartridge 200 includes a casing 202 which contains a toner 201, a toner stirring section 203 which stirs and conveys the toner 201, and a toner replenishing roller 204 which is provided above an upper surface of the toner 201.
The toner stirring section 203 is rotatably supported by the casing 202 around a predetermined axis J203. Specifically, included are a cylindrical shaft section 211 extending along the axis J203, two plate-like stirring blades 212a and 212b which are provided in a protruding state on an outer circumferential surface of the shaft section 211 and departing from each other in a circumferential direction by 180 degrees, and a conveying sheet 213 which is a sheet-like member having flexibility and provided by being fixed to a loose end part of the stirring blade 212a that is one of the blades.
The toner stirring section 203 which is configured in this manner is rotated in a direction of an arrow R3 by a motor (not shown) mounted on the main body of the image forming apparatus. The toner stirring section is configured so that the stirring blades 212a and 212b stir the toner 201 which is contained in the casing 202 and so that the conveying sheet 213 conveys the toner 201 to the toner replenishing roller 204 which is provided on a rear stage side. In particular, the conveying sheet 213 is provided so as to scoop a part of the toner 201 contained in the casing 202 and throw the scooped toner 201 toward the toner replenishing roller 204, and thereby convey the toner 201 to the toner replenishing roller 204.
In addition, the toner replenishing roller 204 extends along an axis J204 which is parallel to the axis J203, and is rotatably supported by the casing 202 around the axis J204. The toner replenishing roller 204 is provided adjacent to a toner replenishing port 205 which is formed on the casing 202. The toner replenishing roller 204 is rotated in a direction of an arrow R4 by a motor (not shown) which is mounted on the main body of the image forming apparatus. The toner replenishing roller 204 is rotated in the rotational direction R4 and thereby supplies the toner 201 that has been conveyed by the toner stirring section 203 to a developing device (not shown) which is mounted on the main body of the image forming apparatus though the toner replenishing port 205.
Usually, an unused toner cartridge 200 is packed in a box and kept in an empty space or a depository until it becomes necessary to replace a toner cartridge. In addition, a position of the toner cartridge 200 during keeping is diverse. For example, the toner cartridge 200 is kept in a position similar to a position in a state attached to the image forming apparatus (hereinafter, also referred to as “horizontal position”) in some cases, or kept in a position where the axis J203 is parallel to a vertical direction (hereinafter, also referred to as “vertical position”) in other cases.
In any case, the toner 201 contained in the casing 202 is in a compressed state by gravity acting on the toner 201 when kept in a state of maintaining a fixed position over a long term. In particular, it is likely to become a more compressed state when kept in the vertical position compared to being kept in the horizontal position. In addition, a toner agglomerate of aggregated toner particles is likely to be generated depending on an environment in which the toner cartridge 200 is kept.
As shown in FIG. 16, in the toner cartridge 200 in an initial state, since a large amount of the toner 201 is contained in the casing 202, a part of the toner stirring section 203 is provided in a state of being immersed in the toner 201. Accordingly, when kept in the state of maintaining a fixed position over a long term, the conveying sheet 213 immersed in the toner 201 is surrounded by the compressed toner 201, and in some cases, toner particles aggregate to attach to the surface of the conveying sheet 213.
When the conveying sheet 213 is surrounded by the toner 201 in the compressed state, an extremely large load is to act on the conveying sheet 213. In other words, the conveying sheet 213 in the state of being immersed in the toner 201 is in the state where it is hard to displace.
In such a case, it is necessary to impart extremely large torque for the toner stirring section 203 in order to rotate the toner stirring section 203. That is, a load applied to the motor increases in order to rotate the tonner stirring section 203 in such a case.
When the load on the motor increases in this way, there is a possibility that the motor loses synchronism or is broken. Accordingly, in order to avoid such a failure, an existing main body of the image forming apparatus is mounted with a motor capable of generating large torque in advance.
However, the load on the motor increases most, in other words, the torque required for rotating the toner stirring section 203 increases most when rotating the toner stirring section 203 in the toner cartridge 200 in the initial state, and after the toner 201 in the compressed state is disintegrated with a rotation of the toner stirring section 203, torque needed for rotatable driving does not increase so much.
That is, the existing main body of the image forming apparatus is mounted with a motor capable of generating large torque only to avoid a failure generated for the toner cartridge 200 in the initial state. Accordingly, there is a problem that the existing main body of the image forming apparatus has an extremely uneconomical configuration.
Japanese Unexamined Patent Publication JP-A 2001-290350 discloses that a toner aggregate included in a toner contained in a casing of a toner replenishing apparatus is pulverized by a pulverizing member which is provided to stand on an inner wall of the casing and whose leading end is formed in a concavo-convex shape and an agitator for pulverizing the toner aggregate whose leading end is formed in a concavo-convex shape which fits the concavo-convex shape. However, in JP-A 2001-290350, there is no consideration as to a failure which is generated during the initial rotation as described above.